Two years ago, the three low-rise apartment buildings at the intersection of Southern Avenue and Benning Road in Washington, D.C., stood derelict and abandoned, uninhabitable reminders of 1960s brick and block construction. Today, the buildings—now known as Weinberg Commons—represent a landmark effort to provide clean, secure and energy-efficient shelter to low-income families. For the scores of people—architects, energy consultants, contractors and experts in housing finance, to name a few—who helped repurpose Weinberg Commons and bring it back to life, this project represents an unparalleled achievement in retrofitting. For the families who now live here, it means a giant step toward a more secure future.

Thermal conductivity, air infiltration and exfiltration, and solar gain were important to the team working on Weinberg Commons.

One of the keys to that secure future will be very low or no energy bills. From the beginning, the team that oversaw the retrofitting of these buildings, each with almost 8,000 square feet of rentable space, was committed to ensuring that all three would show greatly reduced energy use and at least one would achieve Passive House (PH) certification.

The criteria to become a passive structure are rigorous and focus on three specific design elements to reduce energy. (The requirements and certification observed by the Weinberg Commons team are set by Chicago-based PHIUS, the Passive House Institute U.S.)

The first requirement is airtightness to ensure the building minimizes the amount of heated or cooled air it loses (0.6 air changes per hour at 50 Pascals of pressure).

Second, a Passive House cannot use more than 4.75 kBtu per square foot per year. This is specific heating energy demand (or cooling in cooling climates).

The third requirement caps the peak total amount of energy the heating and cooling system and appliances in the building can use per year, including domestic hot water, lighting and plug loads. It cannot exceed 38 kBtu per square foot per year.

Three low-rise apartment buildings at the intersection of Southern Avenue and Benning Road in Washington, D.C., stood derelict and abandoned, uninhabitable reminders of 1960s brick and block construction.

Michael Hindle, a Baltimore-based Certified Passive House Consultant who is current president of the Passive House Alliance U.S. Board of Managers, helped with the retrofit design of Weinberg Commons. (Passive House Alliance U.S. is a PHIUS program designed to advance passive building.) He points out these three pass/fail criteria are measures of success, not design principles to help a team achieve the energy savings that lead to PH certification. However, Hindle highlights five design principles have been identified as important guides in the design of Passive House projects:

Continuous insulation through the building’s entire envelope without any thermal bridging.

An extremely tight building envelope, preventing infiltration of outside air and loss of conditioned air.

High-performance windows and doors, typically triple-paned.

Balanced heat- and moisture-recovery ventilation and a minimal space-conditioning system.

Solar gain is optimized to exploit the sun’s energy for heating purposes and minimize it in cooling seasons.

Although only one building at Weinberg Commons has achieved PH certification, all three buildings were designed to the exact same specifications and technically could be PH certified as long as the rigorous airtightness threshold is met. Several factors influenced the decision, made at the outset of the project, to focus on just one building for PH certification. The design team’s perception was that airtightness would be the most challenging aspect for the contractor. Matt Fine, an architect with Zavos Architecture & Design, Frederick, Md., who led the project, explains: “The intention was to proceed with the first building, test its airtightness and improve on that scope of work for the next building. Repeat, refine and finally apply to the third sequential building.”

Fine points out the first two buildings actually achieved “super” airtightness results relative to any new-construction project built today but did not cross the 0.6 air changes per hour at 50 Pascals of pressure threshold of Passive House. Given the budget-conscious nature of the Weinberg Commons project, resealing and retesting of the first two buildings was not an option for the team, but lessons learned from these two buildings were applied to the retrofit of the third building. “In retrospect, all three buildings would have been able to meet the PH threshold with relatively little extra effort,” Fine says. “But the dynamics of construction sequencing, along with imposed schedules for occupancy, complicated our ability to be flexible with scope change once the contracts were executed and limited dollars were allocated.”

Six passive townhomes that are part of Habitat for Humanity’s Ivy City community of Northeast Washington are including 8 inches of polyiso insulation on the roof. These passive townhouses are designed to reduce overall energy consumption by 70 percent and heating and cooling demand by 80 to 90 percent.

The six townhouses are being built to meet the Passive House Institute US (PHIUS) Passive House specifications. Founded in 2007, PHIUS is the leading certifier of passive buildings.

“The Ivy City townhouses show the role high-performance insulation plays in the built environment, particularly when it comes to designing homes that are more affordable to operate,” said Jared Blum, president of the Polyisocyanurate Insulation Manufacturers Association (PIMA). “We are proud to be involved with this Habitat for Humanity project that will provide much needed affordable housing in the nation?s capital.”

PIMA member companies—Atlas Roofing, Firestone Building Products, GAF, Hunter Panels, JM, and R-max—donated the polyiso for this project in celebration of the association’s 25th anniversary.

“The passive house model embodies Habitat for Humanity’s vision that all people deserve safe, comfortable, affordable and sustainable housing, and the polyiso insulation contributes to that vision,” said Andrew Modley, production manager, Habitat for Humanity of Washington, D.C. “Passive housing will provide our homeowner families with an ability to consume significantly less energy overall by using passive integrated design, climate appropriate insulation, and airtight construction. These benefits will not only save the homeowners money, but will empower them to create a more sustainable lifestyle.”

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November/December 2018

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Roofing is a national publication that unravels, investigates and analyzes how to properly design, install and maintain a roof system. Through the voices of professionals in the field, Roofing’s editorial provides a unique perspective.